The proposed research will examine, in rats, the relationship between neurological change in the hippocampal formation which is associated with senescence, and the accompanying decline of spatial learning-memory performance. Three main areas of neurophysiological study will be covered: synaptic transmission and its modification through experience; postsynaptic integraion and electrical excitability; and analysis of single unit activity in the intact freely moving animal. The methods will involve extra- and intracellular stimulation and recording in the in vitro hippocampal slice, and extracellular techniques in both the acute (anesthetized) and chronicaly prepared (unrestrained) animal. Behavioral tests of spatial perception and memory (known to require an intact hippocampus for their proper performance) will be carried out in conjunction with some of the neurophysiological experiments. The long-term goal of this project is a more complete understanding of the biological basis for the deterioration of cognitive function known to occur in the elderly; a prerequisit for development of effective therapeutic measures.